1. Field of the Invention
The disclosure relates generally to containment systems for storage tanks and, more specifically, to a containment system for providing continuous monitoring, corrosion protection, and improved leak detection of both the containment system and the storage tank.
2. Description of the Related Art
Concern for environmental pollution has resulted in additional governmental requirements to prevent certain chemicals stored in tanks from leaking into the environment. In particular, for several types of fluids, federal, state and local regulations require double containment systems for the protection, for example, of groundwater. Many commonly known methods of protecting steel tanks against corrosion have been used. For example, connecting piping of different metals can be electrically isolated to prevent the development of corrosive currents. Also, the inside and outside of the steel tank can be coated with a protective material. Additionally, cathodic protection can be employed, which uses a sacrificial anode to reverse corrosive underground current flow by placing an impressed current on the tank Many steel tanks have a layer of sand between the outer tank and the inner tank for absorption of leaks, and to support the inner tank. One technique to monitor corrosion has been to introduce a negative pressure (i.e., a partial vacuum) between the inner tank and the outer tank. However, because of the substantial distance between the inner tank and the outer tank, for example, because of the layer of sand, the vacuum effect is less than desired.
Other types of tanks employ the use of non-metallic liners. Thus, whereas the outer tank may be formed from a metal, e.g., steel, the inner tank is formed from a non-metallic material, such as fiberglass or other composite. An issue with non-metallic liners is that most non-metallic materials do not have the same toughness, compression resistance, and impact resistance as that of many metals. As a result, the non-metallic materials are more prone to cracking in certain instances. Moreover, because of the physical characteristics of the non-metallic materials used for the liner, use of a negative pressure between the outer tank and the non-metallic liner has been discouraged because the negative pressure tends exacerbate the problems associated with the non-metallic liner.
Another issue associated with current containment systems and the monitoring of leaks within these systems is the inability to narrow the potential location of a leak once a leak has been detected. For example, when a negative pressure is introduced between the inner and outer tanks, a change in the negative pressure is an indication of a leak. However, current systems cannot establish the general location within the tank where the leak exists or whether the leak is in the inner tank or the outer tank.
There is, therefore, a need for a containment system that is capable of identifying where within the storage tank a leak may exist and whether the leak exists in the inner tank or the outer tank. Also, a need exists to minimize leaks within the inner and outer tanks by reducing corrosion of the inner and outer tanks.